Semiconductor device and method for the fabrication thereof

ABSTRACT

This invention pertains to a method for forming thin films on substrates wherein the films are produced by applying a solution of an electrically insulating, heat-curing resin onto the substrate, evaporating the solvent and exposing the resin to high energy radiation to cure the resin. The resin solution contains a substance selected from solvents and gas generating additives that causes the dedensification of the film during the cure of the resin. This results in a film having a dielectric constant of below 2.7. This invention also pertains to a semiconductor device having an interconnect structure comprising at least one electrically conductive layer with an interposed insulating layer having a dielectric constant of less than 2.7 wherein the insulating layer is produced by the method of this invention.

FIELD OF THE INVENTION

[0001] This invention pertains to a process for the formation ofelectrically insulating films having low dielectric constants and tosemiconductor devices that have an interconnect structure comprising atleast one electrically conductive layer with an interposed insulatinglayer. The invention also relates to methods for the fabrication ofsemiconductor devices of this type.

BACKGROUND OF THE INVENTION

[0002] The increasing miniaturization of semiconductor elements (theincreasingly high degree of integration of semiconductor devices) hasled to the use of multilevel interconnect structures on semiconductorsubstrates. In order to reduce parasitic capacitance between conductors,material consisting mainly of silicon oxide is generally used for theinsulating layers in such semiconductor devices.

[0003] Insulating thins films of silica are known for use as protectivelayers and as insulating layers in electronic devices. The use ofwet-coating compositions to form the layers is generally well known. Forexample, U.S. Pat. No. 4,756,977 teaches a process for coatingelectronic devices with a silica thin film by applying a solventsolution of hydrogen silsesquioxane resin on a substrate, evaporatingthe solvent, and then heating at temperatures of 150° C. to 1000° C. toeffect conversion into ceramic like silica.

[0004] It is also known that the dielectric constant of the insulatingthin film can be reduced by executing the insulating thin film itself asa porous structure. For example, U.S. Pat. No. 5,548,159 has describedthe formation of an insulating thin film with a porous structure throughthe use of the baked product of hydrogen silsesquioxane resin as thedielectric layer in a highly integrated circuit. This patent, however,does not disclose a specific method for the formation of the porousstructure.

[0005] Because the miniaturization of semiconductor elements leads toincreasingly small interconnect gaps and increasingly high aspect ratiosbetween interconnects, large film thicknesses and an excellent capacityto fill between interconnects are required of the insulating layers.Highly integrated circuits with interconnect gaps declining below 0.18μm have been designed for semiconductor devices in recent years. Whilehighly integrated circuits of this type require that the dielectricconstant of the insulating layers be brought below 2.7, even insulatinglayers formed from hydrogen silsequioxane resin have been unable toachieve such dielectric constants.

[0006] An object of this invention is to provide a process for forminginsulating thin films that have a low dielectric constant.

[0007] A further object of this invention is to provide semiconductordevices having low dielectric constant insulating layers therein and tothe method for the fabrication thereof.

SUMMARY OF THE INVENTION

[0008] This invention pertains to a method for forming electricallyinsulating thin films wherein the method comprises coating the surfaceof a substrate with a composition comprising

[0009] (A) a resin selected from the group consisting of electricallyinsulating, heat-curing organic resins and electrically insulating,heat-curing inorganic resins; and

[0010] (B) a solvent capable of dissolving resin (A) and

[0011] (C) a solvent whose boiling point or vapor pressure curve oraffinity for resin (A) differs from that of solvent (B);

[0012] evaporating at least a portion of the solvents (B) and (C); andsubsequently exposing the substrate to high energy radiation andinducing evaporation of the remaining solvents during the course of orafter the cure of resin (A).

[0013] This invention also pertains to a method for forming electricallyinsulating thin films wherein the method comprises coating the surfaceof a substrate with a composition comprising

[0014] (A) a resin selected from the group consisting of electricallyinsulating, heat-curing organic resins and electrically insulating,heat-curing inorganic resins; and

[0015] (B) a solvent capable of dissolving the resin (A); and

[0016] (D) a substance that is soluble in solvent (B) and that cangenerate gas in the temperature range of from 0° C. to 800° C. byheating or by interaction with resin (A);

[0017] evaporating the solvent (B); and subsequently exposing thesubstrate to high energy radiation and inducing the generation of gasfrom the substance (D) during the course of or after the cure of theresin (A).

[0018] The processes of this invention results in a porosification ordedensification of the thin film and reduction in the dielectricconstant to below 2.7. This makes possible an adequate attenuation inthe parasitic capacitance between interconnects for semiconductordevices in which an interconnect structure comprising at least oneelectrically conductive layer is provided on the surface of asemiconductor substrate with separation by an interposed electricallyinsulating layer—even in the case of highly integrated circuits in whichthe interconnect gap is narrower than 0.18 μm.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a cross-sectional diagram that shows the variousprocesses in the fabrication of a semiconductor device that is anexemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The inorganic or organic resin (A) used in the present inventionis not critical as long as it is solvent soluble, can be cured byheating after its application, and provides insulation. Resin (A) can beexemplified by inorganic resins such as silica precursor resins, forexample, hydrogen silsesquioxane resin, the partial hydrolyzates ofalkoxysilanes, and others; and by organic resins such as polyimideresins, fluorocarbon resins, benzocyclobutene resins, and fluorinatedpolyallyl ethers. Resin (A) can take the form of a single resin or amixture of two or more resins. Silica precursor resins (with theircapacity to cure into silica) are preferred for their ability to provideparticularly good insulating properties. Among the silica precursorresins, hydrogen silsesquioxane resins, which can be used in anon-etchback process, are particularly preferred.

[0021] The hydrogen silsesquioxane resin is a polysiloxane whose mainskeleton is composed of the trifunctional siloxane unit HSiO_(3/2) andis a polymer with the general formula (HSiO_(3/2))_(n) in which thesubscript n is an integer. Hydrogen silsesquioxane resins can becategorized based on their molecular structure into ladder-typepolysiloxanes and cage-type polysiloxanes. The terminals of theladder-type polysiloxanes can be endblocked by, for example, thehydroxyl group, a triorganosiloxy group such as the trimethylsiloxygroup, or a diorganohydrogensiloxy group such as thedimethylhydrogensiloxy group. Hydrogen silsesquioxane resin can besynthesized, for example, by the hydrolysis of trichlorosilane andensuing polycondensation (see U.S. Pat. No. 3,615,272 and JapanesePatent Applications Laid Open (Kokai or Unexamined) Numbers Sho59-189126 (189,126/1984) and Sho 60-42426 (42,426/1985)).

[0022] Solvent (B) should be capable of dissolving resin (A) without theoccurrence of chemical changes, but is not otherwise critical. Solventsusable as the solvent (B) are exemplified by aromatic solvents such astoluene, xylene, and others; aliphatic solvents such as hexane, heptane,octane, and others; ketone solvents such as methyl ethyl ketone, methylisobutyl ketone, and others; aliphatic ester solvents such as butylacetate, isoamyl acetate, and others; and silicone solvents such aschain methylsiloxanes like hexamethyldisiloxane and1,1,3,3-tetramethyldisiloxane, cyclic siloxanes like1,1,3,3,5,5,7,7-octamethyltetracyclosiloxane and1,3,5,7-tetramethyltetracyclosiloxane, and silanes such astetramethylsilane and dimethyldiethylsilane. Methyl isobutyl ketone andthe silicone solvents are preferred.

[0023] Solvent (C) is solvent that has at least one characteristicselected from the boiling point, vapor-pressure curve, and affinity forthe resin that differs from the corresponding characteristic of thesolvent (B). A solvent with a boiling point higher than that of thesolvent (B) is preferred. Solvent (C) is exemplified by (the value inparentheses is the boiling point): hydrocarbon solvents such asamylbenzene (202° C.), isopropylbenzene (152° C.), 1,2-diethylbenzene(183° C.), 1,3-diethylbenzene (181° C.), 1,4-diethylbenzene (184° C.),cyclohexylbenzene (239° C.), dipentene (177° C.),2,6-dimethylnaphthalene (262° C.), p-cymene (177° C.), camphor oil(160-185° C.), solvent naphtha (110-200° C.), cis-decalin (196° C.),trans-decalin (187° C.), decane (174° C.), tetralin (207° C.),turpentine oil (153-175° C.), kerosene (200-245° C.), dodecane (216°C.), branched dodecylbenzene, and others; ketone and aldehyde solventssuch as acetophenone (201.7° C.), isophorone (215.3° C.), phorone(198-199° C.), methylcyclohexanone (169.0-170.5° C.), methyl n-heptylketone (195.3° C.), and others; ester solvents such as diethyl phthalate(296.1° C.), benzyl acetate (215.5° C.), γ-butyrolactone (204° C.),dibutyl oxalate (240° C.), 2-ethylhexyl acetate (198.6° C.), ethylbenzoate (213.2° C.), benzyl formate (203° C.), and others;sulfur-containing compound solvents such as diethyl sulfate (208° C.),sulfolane (285° C.), and others; halohydrocarbon solvents; alcoholsolvents; etherified hydrocarbon solvents; carboxylic anhydridesolvents; phenolic solvents; and silicone solvents.

[0024] In the case of the insulating thin film-forming composition inwhich resin (A) is dissolved in solvents (B) and (C), the solvents (B)and (C) are not simply employed as solvents for the resin. Rather, thesolvents (B) and (C) are also gasified and expelled from the systemduring or after resin cure, thereby leaving voids or free spaces in theinsulating thin film and as a result generating a low dielectricconstant insulating thin film. A major fraction of the main solvent (B)will evaporate immediately after coating on the substrate, but a portionwill remain in the film and this residual component functions to formvoids. However, in order to efficiently lower the dielectric constant,solvent (C) must be added in addition to the solvent (B). Solvent (C) isone or a mixture of 2 or more solvents that have a higher boiling pointthan the solvent (B), or that have a different vapor-pressure curve fromthat of the solvent (B), i.e., that are more difficult to evaporate, orthat have a different affinity for the resin from that of the solvent(B). Solvent (C) remains in larger amounts in the film immediately afterthe composition has been coated on the substrate and will also beevaporated and expelled from the system during or after resin cure.Solvent (C) is not crucial, but it should be selected with a view toobtaining an optimal relationship with the curing temperature of theresin.

[0025] Additive (D), which is a source of gas generation, is one or amixture of two or more substances that are soluble in solvent (B) andthat can generate gas in the temperature range from 0° C. to 800° C. byheating or by interaction with the resin. “Gas generation” refers to thegeneration of gas by volatilization, the generation of gas by anautonomous decomposition reaction, and the release of gas by chemicalreaction with the resin.

[0026] In the case of the insulating thin film-forming composition inwhich resin (A) is dissolved along with the substance (D) in the solvent(B), through heating or by interaction with the resin the substance (D)generates gas, preferably also with expulsion from the system, during orafter resin cure. The effect of this gas generation, preferably alsowith expulsion from the system, is to leave voids or free spaces in theinsulating thin film and thereby lower the dielectric constant of theinsulating thin film. The temperature at which gas is generated from thesubstance (D) must be compatible with the process for forming insulatingthin films and will be in the range from 0° C. to 800° C. and ispreferably from 25° C. to 400° C. Since in a preferred embodiment amajority of the solvent (B) evaporates immediately after coating on thesubstrate and gas generation from the substance (D) occurs subsequent tothis, the onset temperature for gas generation from substance (D) ispreferably higher than the boiling point of the solvent (B).

[0027] Additives (D) that generate gas by volatilization are exemplifiedby, but not limited to, organic solids such as biphenyl, naphthalene,anthracene, and the like, and by oils such as silicone oils and thelike. When hydrogen silsesquioxane resin is used as the resin, siliconeis preferred based on compatibility considerations.

[0028] Additives (D) that generate gas by their own decomposition areexemplified by, but not limited to, organic peroxides such as benzoylperoxide and the like.

[0029] Additives (D) that generate gas by interaction with the resin canbe exemplified by amines, for example,N,N,N′,N′-tetramethyl-1,6-hexanediamine, when the resin contains SiH, inwhich case hydrogen gas is generated.

[0030] The resin coated on the substrate is cured by exposure to highenergy radiation such as electron beam, ultraviolet radiation, x-rays,and others. A single type of radiation can be used or several types ofradiation can be used in combination. The use of exposure to high energyradiation permits resin cure to be induced while restraining thetemperature to low levels.

[0031] The ability to induce resin cure at low temperatures through theuse of exposure to high energy radiation as described above permits useas the resin of low molecular weight hydrogen silsesquioxane resin witha molecular weight≦1,500. Low molecular weight hydrogen silsesquioxaneresin of this type offers the advantages of an excellent capacity tocoat and planarize the substrate and an excellent capacity to fill inand embed topographical variations on the substrate caused, for example,by interconnects. At the same time, however, exposure to hightemperatures causes resin of this type to scatter out, resulting incontamination of surrounding equipment and a diminution in filmthickness. As a consequence, it has been necessary in the case ofthermal curing, for example, in an oven, to preliminarily remove the lowmolecular weight component from hydrogen silsesquioxane resin. However,the use of exposure to high energy radiation permits the use of lowmolecular weight hydrogen silsesquioxane resin.

[0032] The atmosphere for the resin curing reaction is also notcritical, and, in addition to nitrogen and oxygen atmospheres, thecuring reaction may be run in special atmospheres such as water vapor,ammonia, nitrogen monoxide, and ozone.

[0033] When the high energy radiation takes the form of the electronbeam, exposure can be carried out at ambient pressure or at reducedpressure. In the case of irradiation at ambient temperature, theatmosphere is not critical and exposure can be carried out under theatmospheres already described above. In the case of irradiation atreduced pressure, the degree of the vacuum is again not critical andirradiation can be carried out at any pressure ranging from ultrahighvacuums to vacuums near ambient pressure. In addition, when exposure iscarried out under reduced pressure and in particular when the specimenis held at reduced pressure immediately after exposure under a highvacuum, the dangling bonds that have been produced in the insulatingthin film can be preserved. Under these circumstances, the admission ofany of various gases to the specimen with a drop in the degree of vacuummakes possible bonding or substitution of the dangling bonds with thegas molecules and hence the utilization of post-irradiation reactionsfor film formation.

[0034] The crosslinking arising from the curing reaction can be, forexample, crosslinking based on the condensation reaction ofsilicon-bonded hydrogen, crosslinking based on the addition reactionbetween silicon-bonded hydrogen and silicon-bonded vinyl groups, andcrosslinking based on the condensation reaction of alkoxy groups andsilanol groups as seen in the known types of inorganic and organic SOGs.Taking these into consideration, the composition for forming insulatingthin films may contain an appropriately selected additive for thepurpose of accelerating the curing reaction induced by the high energyradiation. The cure accelerator can be, for example, aplatinum-containing compound such as chloroplatinic acid hexahydrate andshould be selected as appropriate as a function of the type of highenergy radiation.

[0035] The thin films produced by the method of this invention may beused in the fabrication of semiconductor devices. As shown in FIG. 1(a),fabrication commences with the formation of a base insulating layer 2 ona semiconductor substrate 1 (silicon wafer) on the surface of which asemiconductor element (not shown) has been formed. This can be done bylaying down, for example, a BPSG film over the entire surface of thesemiconductor substrate 1 and reflowing this film. An electricallyconductive layer is then formed by sputtering a metal, for example,aluminum, on the base insulating layer 2. Lower level interconnects 3 a,3 b, and 3 c are thereafter formed by patterning the conductive layer byknown methods.

[0036] As shown in FIG. 1(b), an insulating layer 4 is subsequentlyformed by coating, for example, by spin coating, the entire surface ofthe semiconductor substrate 1 with the thin film forming composition andsubsequently curing the resin by exposure to high energy radiation.During this process, the generation of gas is induced within theinsulating layer 4 during the course of or after resin cure, and thisgas generation causes a dedensification of the insulating layer 4. Thisdedensification occurs as the development of porosity in the insulatinglayer 4 or as an increase in the free space in the insulating layer 4.

[0037] As shown in FIG. 1(c), through holes 5 that reach, for example,to the lower level interconnects 3 a and 3 c, are then provided bymasking with a photoresist and selectively etching the insulating layer4 that overlies, respectively, the lower level interconnects 3 a and 3c. A conductive layer is then formed over the entire surface bysputtering a metal, for example, aluminum. This is followed by etchbackby plasma etching until exposure of the insulating layer 4, which leavesinterlevel interconnects within the through holes 5.

[0038] As shown in FIG. 1(d), the upper level interconnects 6 a and 6 band the insulating layer 7 are then formed on the etchbacked surface bythe same methods as used to provide the lower level interconnects 3 a to3 c and insulating layer 4. The preceding steps result in the formationof a multilevel interconnect structure of lower level interconnects 3 ato 3 c and upper level interconnects 6 a and 6 b on the semiconductorsubstrate 1 wherein the interconnects are electrically insulated by thebase insulating layer 2 and the interlayer insulating layers 4 and 7.The fabrication method described hereinabove makes it possible to bringthe dielectric constant of the dedensified insulating layer 4 to below2.7.

[0039] In order to reduce the dielectric constant of the insulatinglayer to below 2.7, it is necessary in the present invention to lowerthe density of the insulating layer by increasing the porosity or freespace. However, the development of this porous character must not beaccompanied by negative influences on the film strength, dielectricbreakdown, adherence, or moisture absorption. As a consequence, theresin of the insulating layer is preferably hydrogen silsesquioxaneresin, which is a silicon dioxide precursor.

[0040] After the resin solution has been coated on the semiconductorsubstrate and the solvent has been removed, the resin may be melted inorder to fill in topographical variations on the semiconductor substrateand planarize depressions and elevations in the insulating layer. Inthis case, a resin is preferably used that has a melting point orsoftening point.

[0041] When the resin solution does not contain additive (D), gasgeneration after the beginning of resin cure will be brought about bythe solvent. When the resin solution contains additive (D), gasgeneration after the beginning of resin cure will be brought about bythe additive or solvent. In either case, gas generation must occur afterthe beginning of resin cure. When the gas generation process occurs withthe resin in uncured form, problems will develop such as cracking in theultimately obtained insulating layer and a failure to obtain aninsulating layer with the desired thickness due to dissolution by theresin.

[0042] In order to cause gas generation after initiation of resin cure,chemical stabilization of the solvent or additive at the cure initiationtemperature can be achieved by establishing a high temperature for theinitiation of gas generation and/or establishing a low temperature forthe initiation of resin cure. The gas generation preferably occurs aftera moderate cure but prior to complete cure. The occurrence of gasgeneration prior to complete cure permits an effective development ofporosity in the insulating layer.

[0043] The gas generation may be carried out at reduced pressure. Theexecution of gas generation at reduced pressure can accelerate gasgeneration. In addition to conducting gas generation by heating, it mayalso be carried out with the impression of ultrasound or microwaves(e.g., electromagnetic radiation). The execution of gas generation bythe impression of microwaves makes it possible to lower the treatmenttemperatures in the overall fabrication process. After gas generation,resin cure can be developed further by heating or exposure to highenergy radiation. The treatment temperature in this process can bereduced through the use of high energy radiation.

[0044] The gas generation can be, for example, volatilization (simplegasification); gasification reactions such as decomposition reactionsand chemical reactions (also including reactions with the resin);sublimation; and gasification after liquefaction of a solid. Additives(D) that undergo gasification or decomposition and leave no residues inthe system after gas generation are preferred since they will have nonegative influences on the semiconductor device.

[0045] The dielectric constant of the insulating layer can be broughtbelow 2.7 by coating the semiconductor substrate with a solution oforganic resin and/or inorganic resin dissolved in solvent and formingthe insulating layer by curing the said resin by exposure to high energyradiation while dedensifying the insulating layer through the generationof gas within the insulating layer after the beginning of resin cure.This makes possible an adequate attenuation in the parasitic capacitancebetween interconnects in semiconductor devices in which an interconnectstructure comprising at least one electrically conductive layer isprovided on a semiconductor substrate with separation by an interposedelectrically insulating layer—even in the case of highly integratedcircuits in which the interconnect gap is narrower than 0.18 μm.

EXAMPLES

[0046] So that those skilled in the art can understand and appreciatethe invention taught herein, the following examples are presented, itbeing understood that these examples should not be used to limit thescope of this invention found in the claims.

[0047] The conversion to silica was evaluated by measuring the %residual Si—H bond in the insulating layer by Fourier transform-infraredabsorption spectroscopy (the value immediately after spin coating wasused as 100%).

[0048] The dielectric constant was measured at 25° C./1 MHz on a sampleformed on a silicon wafer with a resistivity of 10⁻² Ω-cm. Themeasurement was run using an impedance analyzer on the capacitancebetween interconnects by the sandwich method with aluminum electrodes.

[0049] Semiconductor devices having an aluminum multilevel interconnectstructure (interconnect pattern with a feature height of 0.5 μm and afeature width and feature interval of 0.18 μm each) base coated with aCVD film were used in Examples 1-7 and Comparative Examples 1 and 2.

EXAMPLE 1

[0050] Molecular weight fractionation was run on hydrogen silsesquioxaneresin with a number-average molecular weight of 1,540 and aweight-average molecular weight of 7,705 (component with molecularweight≦1,500=41%, softening point=90° C.) to give a fraction with anumber-average molecular weight of 5,830 and a weight-average molecularweight of 11,200 (softening point=180° C.). This h-resin fraction wasdissolved in methyl isobutyl ketone to give a solution containing 18weight % solids. To this solution was added cyclohexylbenzene at 1weight % based on the weight of the solution.

[0051] The hydrogen silsesquioxane resin solution was spin coated on thesemiconductor device using a preliminary rotation of 500 rpm for 3seconds and then a main rotation of 5,000 rpm for 10 seconds. After thesolvent was thoroughly evaporated, standing for 10 minutes at roomtemperature gave a film with a thickness of 8,010 angstroms in itsdeepest section. Using an electron beam irradiator with an accelerationvoltage of 165 kV, the wafer was exposed to an electron beam at a doseof 80 Mrad under a current of nitrogen that contained 70 ppm oxygen. Atthis point the insulating layer was less soluble in methyl isobutylketone than immediately after spin coating.

[0052] The wafer was annealed for 1 hour at 400° C. in a quartz furnaceunder a nitrogen current that contained 10 ppm oxygen, withdrawn, andheld for 10 minutes at room temperature. The residual Si—H bond contentin the insulating layer formed on the wafer was 74%, which confirmedthat 26% of the hydrogen silsesquioxane resin had converted to silica.In addition, no abnormalities, such as cracking, etc., were observed inthe insulating layer after conversion.

[0053] After the formation of a CVD film on the insulating layer, amultilevel interconnect structure was elaborated by the via hole contacttechnique. The dielectric constant of the insulating layer in theresulting semiconductor device was 2.5, and no abnormalities inelectrical characteristics were observed.

EXAMPLE 2

[0054] The h-resin fraction described in Example 1 was dissolved inmethyl isobutyl ketone to give a solution containing 18 weight % solids.To this solution was added cyclohexylbenzene at 10 weight % based on theweight of the solution.

[0055] Using the method described in Example 1 the hydrogensilsesquioxane resin solution was spin coated on the semiconductordevice resulting in a film with a thickness of 8,020 angstroms in itsdeepest section. The wafer was exposed to electron beam and annealed asin Example 1. The residual Si—H bond content in the insulating layerformed on the wafer was 73%, which confirmed that 27% of the hydrogensilsesquioxane resin had converted to silica. In addition, noabnormalities, such as cracking, etc., were observed in the insulatinglayer after conversion.

[0056] After the formation of a CVD film on the insulating layer, amultilevel interconnect structure was elaborated by the via hole contacttechnique. The dielectric constant of the insulating layer in theresulting semiconductor device was 2.4, and no abnormalities inelectrical characteristics were observed.

EXAMPLE 3

[0057] The h-resin fraction described in Example 1 was dissolved inmethyl isobutyl ketone to give a solution containing 20 weight % solids.To this solution was added cyclohexylbenzene at 10 weight % based on theweight of the solution.

[0058] Using the method described in Example 1 the hydrogensilsesquioxane resin solution was spin coated on the semiconductordevice except that the main rotation was 4,500 rpm for 10 secondsresulting in a film with a thickness of 13,200 angstroms in its deepestsection. The wafer was exposed to electron beam and annealed as inExample 1. The residual Si—H bond content in the insulating layer formedon the wafer was 74%, which confirmed that 26% of the hydrogensilsesquioxane resin had converted to silica. In addition, noabnormalities, such as cracking, etc., were observed in the insulatinglayer after conversion.

[0059] After the formation of a CVD film on the insulating layer, amultilevel interconnect structure was elaborated by the via hole contacttechnique. The dielectric constant of the insulating layer in theresulting semiconductor device was 2.4, and no abnormalities inelectrical characteristics were observed.

EXAMPLE 4

[0060] The h-resin fraction described in Example 1 was dissolved inmethyl isobutyl ketone to give a solution containing 18 weight % solids.To this solution was added amylbenzene at 10 weight % based on theweight of the solution.

[0061] Using the method described in Example 1 the hydrogensilsesquioxane resin solution was spin coated on the semiconductordevice resulting in a film with a thickness of 8,000 angstroms in itsdeepest section. The wafer was exposed to electron beam and annealed asin Example 1. The residual Si—H bond content in the insulating layerformed on the wafer was 74%, which confirmed that 26% of the hydrogensilsesquioxane resin had converted to silica. In addition, noabnormalities, such as cracking, etc., were observed in the insulatinglayer after conversion.

[0062] After the formation of a CVD film on the insulating layer, amultilevel interconnect structure was elaborated by the via hole contacttechnique. The dielectric constant of the insulating layer in theresulting semiconductor device was 2.4, and no abnormalities inelectrical characteristics were observed.

EXAMPLE 5

[0063] The h-resin fraction described in Example 1 was dissolved inmethyl isobutyl ketone to give a solution containing 18 weight % solids.To this solution was added biphenyl at 10 weight % based on the weightof the solution.

[0064] Using the method described in Example 1 the hydrogensilsesquioxane resin solution was spin coated on the semiconductordevice resulting in a film with a thickness of 8,015 angstroms in itsdeepest section. The wafer was exposed to electron beam and annealed asin Example 1. The residual Si—H bond content in the insulating layerformed on the wafer was 74%, which confirmed that 26% of the hydrogensilsesquioxane resin had converted to silica. In addition, noabnormalities, such as cracking, etc., were observed in the insulatinglayer after conversion.

[0065] After the formation of a CVD film on the insulating layer, amultilevel interconnect structure was elaborated by the via hole contacttechnique. The dielectric constant of the insulating layer in theresulting semiconductor device was 2.4, and no abnormalities inelectrical characteristics were observed.

EXAMPLE 6

[0066] Molecular weight fractionation was performed on a hydrogensilsesquioxane resin with a number-average molecular weight of 1,540, aweight-average molecular weight of 7,705, and a softening point of 90°C. to give a h-resin fraction with a number-average molecular weight of743, a weight-average molecular weight of 1,613, and a softening pointof 25° C. This h-resin fraction was dissolved in a mixed solvent ofhexamethyldisiloxane/octamethyltrisiloxane (30/70 weight %) to give asolution containing 25 weight % solids. To this solution was addedcyclohexylbenzene at 10 weight % based on the weight of the solution.

[0067] Using the method described in Example 1 the hydrogensilsesquioxane resin solution was spin coated on the semiconductordevice except that the main rotation was 3,000 rpm for 10 secondsresulting in a film with a thickness of 8,015 angstroms in its deepestsection. The wafer was exposed to electron beam and annealed as inExample 1 except that the electron beam was at a dose of 160 Mrad. Theresidual Si—H bond content in the insulating layer formed on the waferwas 72%, which confirmed that 28% of the hydrogen silsesquioxane resinhad converted to silica. In addition, no abnormalities, such ascracking, etc., were observed in the insulating layer after conversion.

[0068] After the formation of a CVD film on the insulating layer, amultilevel interconnect structure was elaborated by the via hole contacttechnique. The dielectric constant of the insulating layer in theresulting semiconductor device was 2.2, and no abnormalities inelectrical characteristics were observed.

EXAMPLE 7

[0069] 10 weight % cyclohexylbenzene was added to an organicspin-on-glass (OCD-TYPE7 from Tokyo Oyo Kagaku Kogyo Kabushiki Kaisha)that was a precursor for silicon dioxide.

[0070] Using the method described in Example 1 the organic-spin-on-glasssolution was spin coated on the semiconductor device resulting in a filmwith a thickness of 7,520 angstroms in its deepest section. The waferwas exposed to electron beam and annealed as in Example 1. It wasconfirmed at this point that conversion to silica had occurred. Inaddition, no abnormalities, such as cracking, etc., were observed in theinsulating layer after conversion.

[0071] After the formation of a CVD film on the insulating layer, amultilevel interconnect structure was elaborated by the via hole contacttechnique. The dielectric constant of the insulating layer in theresulting semiconductor device was 2.6, and no abnormalities inelectrical characteristics were observed.

COMPARATIVE EXAMPLE 1

[0072] The h-resin fraction described in Example 1 was dissolved inmethyl isobutyl ketone to prepare a solution containing 18 weight %solids.

[0073] Using the method described in Example 1 the hydrogensilsesquioxane resin solution was spin coated on the semiconductordevice resulting in a film with a thickness of 8,015 angstroms in itsdeepest section. The wafer was annealed for 1 hour at 400° C. in aquartz furnace under a nitrogen current that contained 10 ppm oxygen,withdrawn, and held for 10 minutes at room temperature. The residualSi—H bond content in the insulating layer formed on the wafer was 75%,which confirmed that 25% of the hydrogen silsesquioxane resin hadconverted to silica. In addition, no abnormalities, such as cracking,etc., were observed in the insulating layer after conversion.

[0074] After the formation of a CVD film on the insulating layer, amultilevel interconnect structure was elaborated by the via hole contacttechnique. The dielectric constant of the insulating layer in theresulting semiconductor device was 2.8, and no abnormalities inelectrical characteristics were observed.

COMPARATIVE EXAMPLE 2

[0075] The h-resin fraction described in Example 1 was dissolved inmethyl isobutyl ketone to prepare a solution containing 20 weight %solids.

[0076] Using the method described in Example 1 the hydrogensilsesquioxane resin solution was spin coated on the semiconductordevice except that the main rotation was 4,500 rpm for 10 secondsresulting in a film with a thickness of 13,100 angstroms in its deepestsection. The wafer was annealed for 1 hour at 400° C. in a quartzfurnace under a nitrogen current that contained 10 ppm oxygen,withdrawn, and held for 10 minutes at room temperature. The residualSi—H bond content in the insulating layer formed on the wafer was 75%,which confirmed that 25% of the hydrogen silsesquioxane resin hadconverted to silica. In this case, the post-conversion insulating layersuffered from a substantial decline in film thickness and cracking wasobserved in the insulating layer.

[0077] After the formation of a CVD film on the insulating layer, amultilevel interconnect structure was elaborated by the via hole contacttechnique. The dielectric constant of the insulating layer in theresulting semiconductor device was 2.8. Electrical contact defects wereobserved in parts of the device.

EXAMPLE 8

[0078] Hydrogen silsesquioxane resin was synthesized by the methoddescribed in Example 1 (page 3) of Japanese Patent Publication (Kokoku)Number Sho 47-31838 (U.S. Pat. No. 3,615,272). Analysis of the hydrogensilsesquioxane resin product by gel permeation chromatography (GPC) gavea number-average molecular weight of 1,540 and a weight-averagemolecular weight of 7,705. The hydrogen silsesquioxane resin wassubjected to a molecular weight fractionation according to the methoddescribed in Example 1 (page 5) of Japanese Patent Application Laid Open(Kokai or Unexamined) Number Hei 6-157760 (157,760/1994) (U.S. Pat. No.5,416,190). Analysis of the hydrogen silsesquioxane resin in therecovered fraction (“h-resin fraction”) by GPC gave a number-averagemolecular weight of 5,830 and a weight-average molecular weight of11,200. The conditions in the GPC measurements are reported below.

[0079] instrument: 802A from the Tosoh Corporation

[0080] column: G3000/G4000/G5000/G6000

[0081] carrier solvent: toluene

[0082] column temperature: 30° C.

[0083] molecular weight standard: polystyrene

[0084] detection: differential refractometer

[0085] sample: 2 weight % solids (toluene solution)

[0086] The h-resin fraction was dissolved in methyl isobutyl ketone toprepare the 22 weight % (solids) solution. To this solution was addedcyclohexylbenzene at 1 weight % based on the weight of the solution. Afilm with a thickness of 6,040 angstroms was produced by spin coatingthe solution on a silicon wafer at a preliminary rotation of 500 rpm for3 seconds and then at a main rotation of 3,000 rpm for 10 secondsfollowed by standing for 10 minutes at room temperature. Using anelectron beam irradiator with an acceleration voltage of 165 kV, thewafer was exposed to an electron beam at a dose of 80 Mrad undernitrogen that contained 70 ppm oxygen. At this point the film was lesssoluble in methyl isobutyl ketone than immediately after spin coating.

[0087] The wafer was annealed for 1 hour at 400° C. in a quartz furnaceunder a nitrogen current that contained 10 ppm oxygen, withdrawn, andheld for 10 minutes at room temperature. The residual Si—H bond contentin the resulting insulating film was 74%, which confirmed conversion ofthe hydrogen silsesquioxane resin to silica. In addition, noabnormalities, such as cracking, etc., were observed in the insulatingfilm. The dielectric constant of this insulating film was 2.4.

EXAMPLE 9

[0088] The h-resin fraction prepared in Example 8 was dissolved inmethyl isobutyl ketone to prepare a 22 weight % (solids) solution. Tothis solution was added cyclohexylbenzene at 10 weight % based on theweight of the solution. A film with a thickness of 6,270 angstroms wasproduced by the coating method described in Example 8. The wafer wasthen exposed to electron beam radiation and annealed as in Example 8.The residual Si—H bond content in the resulting insulating film was 74%,which confirmed conversion of the hydrogen silsesquioxane resin tosilica. In addition, no abnormalities, such as cracking, etc., wereobserved in the insulating film. The dielectric constant of thisinsulating film was 2.4.

EXAMPLE 10

[0089] The h-resin fraction prepared in Example 8 was dissolved inmethyl isobutyl ketone to prepare a 35 weight % (solids) solution. Tothis solution was added cyclohexylbenzene at 10 weight % based on theweight of the solution. A film with a thickness of 13,500 angstroms wasproduced by the coating method described in Example 8 except that themain rotation was 2,000 rpm for 10 seconds. The wafer was then exposedto electron beam radiation and annealed as in Example 8. The residualSi—H bond content in the resulting insulating film was 74%, whichconfirmed conversion of the hydrogen silsesquioxane resin to silica. Inaddition, no abnormalities, such as cracking, etc., were observed in theinsulating film. The dielectric constant of this insulating film was2.4.

EXAMPLE 11

[0090] The h-resin fraction prepared in Example 8 was dissolved inmethyl isobutyl ketone to prepare a 22 weight % (solids) solution. Tothis solution was added amylbenzene at 10 weight % based on the weightof the solution. A film with a thickness of 6,150 angstroms was producedby the coating method described in Example 8. The wafer was then exposedto electron beam radiation and annealed as in Example 8. The residualSi—H bond content in the resulting insulating film was 74%, whichconfirmed conversion of the hydrogen silsesquioxane resin to silica. Inaddition, no abnormalities, such as cracking, etc., were observed in theinsulating film. The dielectric constant of this insulating film was2.4.

EXAMPLE 12

[0091] The h-resin fraction prepared in Example 8 was dissolved inmethyl isobutyl ketone to prepare a 22 weight % (solids) solution. Tothis solution was added biphenyl at 10 weight % based on the weight ofthe solution. A film with a thickness of 6,200 angstroms was produced bythe coating method described in Example 8. The wafer was then exposed toelectron beam radiation and annealed as in Example 8. The residual Si—Hbond content in the resulting insulating film was 74%, which confirmedconversion of the hydrogen silsesquioxane resin to silica. In addition,no abnormalities, such as cracking, etc., were observed in theinsulating film. The dielectric constant of this insulating film was2.4.

EXAMPLE 13

[0092] The h-resin fraction prepared in Example 8 was dissolved inmethyl isobutyl ketone to prepare a 22 weight % (solids) solution. Tothis solution was added N,N,N′,N′ -tetramethyl-1,6-hexanediamine at 10weight-ppm based on the weight of the solution. A film with a thicknessof 6,100 angstroms was produced by the coating method described inExample 8. The wafer was then exposed to electron beam radiation andannealed as in Example 8. The residual Si—H bond content in theresulting insulating film was 32%, which confirmed conversion of thehydrogen silsesquioxane resin to silica. In addition, no abnormalities,such as cracking, etc., were observed in the insulating film. Thedielectric constant of this insulating film was 2.4.

EXAMPLE 14

[0093] The h-resin fraction prepared in Example 8 was dissolved inmethyl isobutyl ketone to prepare a 22 weight % (solids) solution. Tothis solution was added benzoyl peroxide at 50 weight-ppm based on theweight of the solution. A film with a thickness of 6,250 angstroms wasproduced by the coating method described in Example 8. The wafer wasthen exposed to electron beam radiation and annealed as in Example 8.The residual Si—H bond content in the resulting insulating film was 35%,which confirmed conversion of the hydrogen silsesquioxane resin tosilica. In addition, no abnormalities, such as cracking, etc., wereobserved in the insulating film. The dielectric constant of thisinsulating film was 2.4.

EXAMPLE 15

[0094] Hydrogen silsesquioxane resin was synthesized by the methoddescribed in Example 1 (page 3) of Japanese Patent Publication (Kokoku)Number Sho 47-31838 (U.S. Pat. No. 3,615,272). Analysis of the hydrogensilsesquioxane resin product by GPC gave a number-average molecularweight of 1,540, a weight-average molecular weight of 7,705, and a valueof 41 weight % for the content of component with a molecular weight nogreater than 1,500. The hydrogen silsesquioxane resin was subjected to amolecular weight fractionation according to the method described inExample 1 (page 5) of Japanese Patent Application Laid Open (Kokai orUnexamined) Number Hei 6-157760 (U.S. Pat. No. 5,416,190). Analysis ofthe hydrogen silsesquioxane resin in the recovered fraction (“h-resinfraction”) by GPC gave a number-average molecular weight of 743, aweight-average molecular weight of 1,613, and a value of 72 weight % forthe content of component with a molecular weight no greater than 1,500.The conditions in the GPC measurements were the same as reported inExample 8.

[0095] This h-resin fraction was dissolved inhexamethyldisiloxane/octamethyltrisiloxane mixed solvent (30/70) toprepare the 30 weight % (solids) solution. To this solution was addedcyclohexylbenzene at 10 weight % based on the weight of the solution. Afilm with a thickness of 6,350 angstroms was produced by the coatingmethod described in Example 8. The wafer was then exposed to electronbeam radiation and annealed as in Example 8. The residual Si—H bondcontent in the insulating film was 72%, which confirmed conversion ofthe hydrogen silsesquioxane resin to silica. In addition, noabnormalities, such as cracking, etc., were observed in the insulatingfilm. The dielectric constant of this insulating film was 2.2.

EXAMPLE 16

[0096] 10 weight % cyclohexylbenzene was added to an organic spin-onglass (brand name: OCD-TYPE7 from Tokyo Oyo Kagaku Kogyo KabushikiKaisha). A film with a thickness of 6,200 angstroms was formed by thecoating method described in Example 8. The wafer was then exposed toelectron beam radiation and annealed as in Example 8. No abnormalities,such as cracking, etc., were observed in the resulting insulating film.The dielectric constant of this insulating film was 2.7.

EXAMPLE 17

[0097] Hydrogen silsesquioxane resin (number-average molecularweight=1,540 and weight-average molecular weight=7,705) synthesizedaccording to the method described in Example 1 (page 3) of JapanesePatent Publication (Kokoku) Number Sho 47-31838 (U.S. Pat. No.3,615,272) was dissolved in methyl isobutyl ketone to prepare the 26weight % (solids) solution. To this solution was added cyclohexylbenzeneat 10 weight % based on the weight of the solution. A film with athickness of 6,100 angstroms was prepared by the coating methoddescribed in Example 8. The wafer was then exposed to electron beamradiation and annealed as in Example 8. The residual Si—H bond contentin the insulating film was 72%, which confirmed conversion of thehydrogen silsesquioxane resin to silica. In addition, no abnormalities,such as cracking, etc., were observed in the insulating film. Thedielectric constant of this insulating film was 2.4.

EXAMPLE 18

[0098] The h-resin fraction described in Example 8 was dissolved inmethyl isobutyl ketone to prepare 22 weight % (solids) solution. To thissolution was added cyclohexylbenzene at 10 weight % and polyoxyethylenelauryl ether at 1 weight %, in each case based on the weight of thesolution. A film with a thickness of 6,350 angstroms was produced by thecoating method described in Example 8. The wafer was then exposed toelectron beam radiation and annealed as in Example 8. The residual Si—Hbond content in the insulating film was 73%, which confirmed conversionof the hydrogen silsesquioxane resin to silica. In addition, noabnormalities, such as cracking, etc., were observed in the insulatingfilm. The dielectric constant of this insulating film was 2.4.

EXAMPLE 19

[0099] The h-resin fraction described in Example 8 was dissolved inmethyl isobutyl ketone to prepare a 18 weight % (solids) solution. Tothis solution was added cyclohexylbenzene at 10 weight % based on theweight of the solution. A film with a thickness of 8,310 angstroms atits deepest section was produced by spin coating the resulting solutionon a polysilicon wafer (feature height=0.5 μm, feature width and featurespacing=0.18 μm) at a preliminary rotation of 500 rpm for 3 seconds andthen a main rotation of 5,000 rpm for 10 seconds and subsequentlyholding for 10 minutes at room temperature. The wafer was heated under anitrogen current on a hot plate using the sequence of 150° C./1 minute,200° C./1 minute, and 250° C./1 minute in the order given. This resultedin fluidization with thorough gapfilling between the features andthorough planarization of the resin surface. Using an electron beamirradiator with an acceleration voltage of 165 kV, the wafer was exposedto an electron beam at a dose of 80 Mrad under nitrogen that contained70 ppm oxygen. At this point the film was less soluble in methylisobutyl ketone than immediately after spin coating. The wafer wasannealed for 1 hour at 400° C. in a quartz furnace under a nitrogencurrent that contained 10 ppm oxygen, withdrawn, and held for 10 minutesat room temperature. No abnormalities, such as cracking, etc., wereobserved in the resulting insulating film.

EXAMPLE 20

[0100] A fluorinated polyallyl ether resin was synthesized according tothe method described on page 116 of the 1995 Proceedings of the TwelfthInternational VLSI Multilevel Interconnection Conference. Analysis ofthe resin product by GPC gave a number-average molecular weight of 2,540and a weight-average molecular weight of 9,390. This resin was dissolvedin methyl isobutyl ketone to prepare the 26 weight % (solids) solution.To this solution was added cyclohexylbenzene at 10 weight % based on theweight of the solution. A film with a thickness of 6,070 angstroms wasproduced by the coating method described in Example 8. The wafer wasthen exposed to electron beam radiation and annealed as in Example 8.This resulted in an additional decline in the solubility of theinsulating film. In addition, no abnormalities, such as cracking, etc.,were observed in the insulating film. The dielectric constant of thisinsulating film was 2.4.

EXAMPLE 21

[0101] The h-resin fraction prepared in Example 8 was dissolved inmethyl isobutyl ketone to prepare a 22 weight % (solids) solution. Tothis solution was added cyclohexylbenzene at 10 weight % based on theweight of the solution. A film with a thickness of 6,270 angstroms wasproduced by the coating method described in Example 8. Using an electronbeam irradiator with an acceleration voltage of 8 kV, the wafer wasexposed for 10 seconds to 5 mC/cm² of radiation under a vacuum of 10⁻⁶torr. The specimen was withdrawn from the vacuum, placed in air atordinary atmospheric pressure, and held for 10 minutes. At this pointthe film was less soluble in methyl isobutyl ketone than immediatelyafter spin coating.

[0102] The wafer was annealed for 1 hour at 400° C. in a quartz furnaceunder a nitrogen current that contained 10 ppm oxygen, withdrawn, andheld for 10 minutes at room temperature. The residual Si—H bond contentin the resulting insulating film was 75%, which confirmed conversion ofthe hydrogen silsesquioxane resin to silica. In addition, noabnormalities, such as cracking, etc., were observed in the insulatingfilm. The dielectric constant of this insulating film was 2.4.

EXAMPLE 22

[0103] The h-resin fraction prepared in Example 8 was dissolved inmethyl isobutyl ketone to prepare a 22 weight % (solids) solution. Tothis solution was added cyclohexylbenzene at 10 weight % based on theweight of the solution. A film with a thickness of 6,310 angstroms wasproduced by the coating method described in Example 8. The wafer wasexposed for 10 minutes to ultraviolet radiation with an intensity of 160W/cm from a high-pressure mercury lamp in air that contained 10 ppmozone. At this point the film was less soluble in methyl isobutyl ketonethan immediately after spin coating.

[0104] The wafer was annealed for 1 hour at 400° C. in a quartz furnaceunder a nitrogen current that contained 10 ppm oxygen, withdrawn, andheld for 10 minutes at room temperature. The residual Si—H bond contentin the resulting insulating film was 71%, which confirmed conversion ofthe hydrogen silsesquioxane resin to silica. In addition, noabnormalities, such as cracking, etc., were observed in the insulatingfilm. The dielectric constant of this insulating film was 2.4.

EXAMPLE 23

[0105] The h-resin fraction prepared in Example 8 was dissolved inmethyl isobutyl ketone to prepare a 22 weight % (solids) solution. Tothis solution was added cyclohexylbenzene at 10 weight % based on theweight of the solution. A film with a thickness of 6,280 angstroms wasproduced by the coating method described in Example 8. While residing ona hot plate heated to 250° C., the wafer was exposed for 10 minutes toultraviolet radiation with an intensity of 160 W/cm from a high-pressuremercury lamp in air that contained 10 ppm ozone. At this point the filmwas less soluble in methyl isobutyl ketone than immediately after spincoating.

[0106] The wafer was annealed for 1 hour at 400° C. in a quartz furnaceunder a nitrogen current that contained 10 ppm oxygen, withdrawn, andheld for 10 minutes at room temperature. The residual Si—H bond contentin the resulting insulating film was 70%, which confirmed conversion ofthe hydrogen silsesquioxane resin to silica. In addition, noabnormalities, such as cracking, etc., were observed in the insulatingfilm. The dielectric constant of this insulating film was 2.4.

COMPARATIVE EXAMPLE 3

[0107] The h-resin fraction described in Example 8 was dissolved inmethyl isobutyl ketone to prepare a 22 weight % (solids) solution. Afilm with a thickness of 6,070 angstroms was produced by the coatingmethod described in Example 8. The wafer was annealed for 1 hour at 400°C. in a quartz oven under a current of nitrogen containing 10 ppmoxygen, then withdrawn and held for 10 minutes at room temperature. Theresidual SiH% in the resulting insulating film was 75%, which confirmedthat conversion of the hydrogen silsesquioxane resin to silica hadoccurred. The production of cracks in the insulating film was alsoobserved. The dielectric constant of this insulating film was 2.8.

COMPARATIVE EXAMPLE 4

[0108] The h-resin fraction described in Example 8 was dissolved inmethyl isobutyl ketone to prepare a 35 weight % (solids) solution. Afilm with a thickness of 13,200 angstroms was produced by spin coatingthe resulting solution on a silicon wafer at a preliminary rotation of500 rpm for 3 seconds and then at a main rotation of 2,000 rpm for 10seconds followed by standing for 10 minutes at room temperature. Thewafer was annealed for 1 hour at 400° C. in a quartz oven under acurrent of nitrogen containing 10 ppm oxygen, then withdrawn and heldfor 10 minutes at room temperature. The residual SiH% in the resultinginsulating film was 75%, which confirmed that conversion of the hydrogensilsesquioxane resin to silica had occurred. Cracks had also beenproduced in the insulating film. The dielectric constant of thisinsulating film was 2.8.

COMPARATIVE EXAMPLE 5

[0109] The h-resin fraction prepared in Example 8 was dissolved inmethyl isobutyl ketone to prepare a 22 weight % (solids) solution. Afilm with a thickness of 6,040 angstroms was produced by the coatingmethod described in Example 8. The wafer was then exposed to electronbeam radiation and annealed as in Example 8. The residual Si—H bondcontent in the insulating film formed on the wafer was 69%, whichconfirmed conversion of the hydrogen silsesquioxane resin to silica. Inaddition, no abnormalities, such as cracking, etc., were observed in theinsulating film. The dielectric constant of this insulating film was2.8. TABLE 1 film thickness in angstroms refractive index residual SiH %after after low- after dielectric after after low- after (degree ofcoating temp. cure annealing constant coating temp. cure annealing filmcure) Example 8 6040 6000 6020 2.4 1.406 1.404 1.363 74 Example 9 62706190 6210 2.4 1.409 1.417 1.365 73 Example 10 13500  13330  13400  2.41.409 1.417 1.361 74 Example 11 6150 6100 6110 2.4 1.415 1.420 1.361 74Example 12 6200 6150 6170 2.4 1.420 1.425 1.365 74 Example 13 6100 62056205 2.4 1.393 1.400 1.369 32 Example 14 6250 6240 6190 2.4 1.393 1.3921.364 35 Example 15 6350 5920 5850 2.2 1.403 1.400 1.360 72 Example 166200 6150 6120 2.7 1.410 1.411 1.369 — Example 17 6100 5950 5900 2.41.411 1.405 1.364 72 Example 18 6350 6300 6210 2.4 1.412 1.407 1.369 73Example 19 8310 8275 8240 — — — — — Example 20 6070 6050 6060 2.4 1.4101.408 1.365 — Example 21 6270 6200 6230 2.4 1.411 1.407 1.366 75 Example22 6310 6250 6210 2.4 1.409 1.407 1.366 71 Example 23 6280 6100 6050 2.41.410 1.401 1.368 70 Comp. Ex. 3 6070 6120 6270 2.8 1.400 — 1.372 75Comp. Ex. 4 13300  13200  13350  2.8 1.392 — 1.372 75 Comp. Ex. 5 60405990 6050 2.8 1.392 1.392 1.379 69

1. A method for forming electrically insulating thin films wherein themethod comprises coating the surface of a substrate with a compositioncomprising (A) a resin selected from the group consisting ofelectrically insulating, heat-curing organic resins and electricallyinsulating, heat-curing inorganic resins; and (B) a solvent capable ofdissolving resin (A) and (C) a solvent selected from the groupconsisting of a solvent whose boiling point differs from solvent (B), asolvent whose vapor pressure curve differs from that of solvent (B) anda solvent whose affinity for resin (A) differs from that of solvent (B)evaporating at least a portion of the solvents (B) and (C); andsubsequently exposing the substrate to high energy radiation andinducing evaporation of the remaining solvents during the course of orafter the cure of resin (A).
 2. The method as claimed in claim 1 whereinthe substrate is an electronic device.
 3. The method as claimed in claim1 wherein the coating of the surface is by spin coating.
 4. The methodas claimed in claim 1 wherein the high energy radiation is electronbeam.
 5. The method as claimed in claim 1 wherein resin (A) is hydrogensilsesquioxane resin.
 6. The method as claimed in claim 1 whereinsolvent (B) is selected from the group consisting of aromatic solvents,aliphatic solvents; ketone solvents, aliphatic ester solvents, siliconesolvents, and silanes.
 7. The method as claimed in claim 1 wherein thesolvent (C) is selected from the group consisting of hydrocarbonsolvents; ketone solvents; aidehyde solvents; ester solvents; diethylsulfate; sulfolane; halohydrocarbon solvents; etherified hydrocarbonsolvents; alcohol solvents; ether solvents; acetal solvents; polyhydricalcohol solvents; carboxylic anhydride solvents; phenolic solvents; andsilicone solvents.
 8. The method as claimed in claim 1 wherein solvent(C) cyclohexylbenzene.
 9. The method as claimed in claim 1 whereinsolvent (C) is amylbenzene.
 10. A method for forming electricallyinsulating thin films wherein the method comprises coating the surfaceof a substrate with a composition comprising (A) a resin selected fromthe group consisting of electrically insulating, heat-curing organicresins and electrically insulating, heat-curing inorganic resins; and(B) a solvent capable of dissolving the resin (A); and (D) at least onesolvent-soluble substance selected from (i) substances that upon heatingat a temperature of from 0° C. to 800° C. generate a gas or; (ii)substances that by interaction with resin (A) generate a gas;evaporating the solvent (B); and subsequently exposing the substrate tohigh energy radiation and inducing the generation of gas from thesubstance (D) during the course of or after the cure of the resin (A).11. The method as claimed in claim 10 wherein the substrate is anelectronic device.
 12. The method as claimed in claim 10 wherein thecoating of the surface is by spin coating.
 13. The method as claimed inclaim 10 wherein the high energy radiation is electron beam.
 14. Themethod as claimed in claim 10 wherein resin (A) is hydrogensilsesquioxane resin.
 15. The method as claimed in claim 10 whereinsolvent (B) is selected from the group consisting of aromatic solvents,aliphatic solvents; ketone solvents, aliphatic ester solvents, siliconesolvents, and silanes.
 16. The method as claimed in claim 10 whereincomponent (D) is an organic solid.
 17. The method as claimed in claim 10wherein component (D) is an organic peroxide.
 18. The method as claimedin claim 10 wherein resin (A) is hydrogen silsesquioxane resin andcomponent (D) is an amine.
 19. A semiconductor device having aninterconnect structure comprising at least one electrically conductivelayer with an interposed insulating layer having a dielectric constantof less than 2.7 wherein the insulating layer is produced by the methodcomprising applying a composition comprising (A) a resin selected fromthe group consisting of electrically insulating, heat-curing organicresins and electrically insulating, heat-curing inorganic resins; and(B) a solvent capable of dissolving resin (A) and (C) a solvent selectedfrom the group consisting of a solvent whose boiling point differs fromsolvent (B), a solvent whose vapor pressure curve differs from that ofsolvent (B) and a solvent whose affinity for resin (A) differs from thatof solvent (B) evaporating at least a portion of the solvents (B) and(C); and subsequently exposing the substrate to high energy radiationand inducing evaporation of the remaining solvents during the course ofor after the cure of resin (A).
 20. A semiconductor device having aninterconnect structure comprising at least one electrically conductivelayer with an interposed insulating layer having a dielectric constantof less than 2.7 wherein the insulating layer is produced by the methodcomprising applying a composition comprising (A) a resin selected fromthe group consisting of electrically insulating, heat-curing organicresins and electrically insulating, heat-curing inorganic resins; and(B) a solvent capable of dissolving the resin (A); and (D) at least onesolvent-soluble substance selected from (i) substances that upon heatingat a temperature of from 0° C. to 800° C. generate a gas or; (ii)substances that by interaction with resin (A) generate a gas;evaporating the solvent (B); and subsequently exposing the substrate tohigh energy radiation and inducing the generation of gas from thesubstance (D) during the course of or after the cure of the resin (A).